The invention relates to antibacterial agents and is particularly concerned with a class of novel cephalosporin derivatives with broad spectrum antibacterial activity, more especially against gram-negative organisms. In particular, the compounds of the invention constitute a series of 7-(.alpha.-aminoarylacetamido)-.DELTA..sup.3 -cephem derivatives having a novel type of acyl group attached to the .alpha.-amino group.
British Pat. No. 1,328,340, published Aug. 30, 1973, describes cephalosporins having the above formula wherein X is a direct carbon-carbon link or a methylene group. However, such compounds as are claimed in the present invention are not structurally obvious over these prior art compounds. Additionally, they exhibit superior antibacterial activity relative to the prior art compounds.